tools/hv: add install target to Makefile

Makefiles usually come with 'install' target included so each distro
doesn't need to implement the procedure from scratch. Add it to tools/hv.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>